Unique roots let plant forage in the snow

作者：龙淫 发布时间：2019-03-08 04:02:01

By Colin Barras (Image: V. G. Onipchenko) High-altitude plants spend a lot of the year covered in thick snow, but one species at least appears to relish its icy canopy. Botanists have discovered that Corydalis conorhiza grows a never-before described network of roots that reach upwards into the overlying snowpack to grab nutrients. This makes the plant the first species known to forage for nutrients in the snow. “It’s remarkable that [the roots] haven’t been noticed before,” says Hans Cornelissen at VU University in Amsterdam, The Netherlands. “But they are easy to miss because they decay rapidly after snow melt and are soon unrecognisable.” After the short growing season and the return of the snow, a new network of roots grows again. Cornelissen and his team made the discovery high in the Caucasus mountains in southern Russia. The ground remains snow-covered except during a short growing season in the height of summer. Exploring the region after the snow melt, Cornelissen’s team discovered that C. conorhiza specimens were surrounded by a thick layer of matted roots growing upwards and out of the soil (see photo, above right). The team realised that the roots, seemingly growing into thin air, would for most of the year be covered in snow – and so they dubbed them “snow roots”. “Snow roots are fundamentally different in structure from soil-dwelling roots, even in the same species,” says Cornelissen. They are much thinner, and rot away soon after exposure to the air. The next step was to work out what the snow roots are for. The team already knew that nitrogen and phosphorus are limiting growing factors in the high-altitude environment, but they found that the standard soil roots of the plant host fungi that give the plant a phosphorus boost. The team reasoned that the unusual roots must be used to gather nitrogen that is trapped in snow flakes as they form. To test the hypothesis they added a traceable isotope of nitrogen in water to snow above C. conorhiza plants. After a few days, the team found that parts of the plant were rich in the isotope. As a control, the team also laced the snow above a dandelion with only soil roots that also grows in the area. They found it didn’t take on any of the foreign nitrogen. Feeding off nitrogen in the snow in this way could give the species an important boost, says Cornelissen. “The growing season is only a few months long, and it really helps to take up nitrogen and translocate it to other parts of the plant before the season actually begins,” he says. “We have some indication from very old literature that an unrelated plant might have the same adaptation,” says Cornelissen. “If that can be confirmed, then snow roots have evolved at least twice independently.” Journal reference: Ecology Letters (in press) More on these topics: